1. Field of the Invention
The present invention relates to a paintable diffusing agent composition containing an impurity diffusion component for being diffused into a semiconductor substrate. Specifically, the invention relates to a diffusing agent composition suitable for being patterned onto a semiconductor substrate surface in an ink-jet method.
2. Description of the Related Art
According to the related art, an N-type impurity diffusion layer in a semiconductor substrate of a solar cell is formed by applying a diffusing agent that contains an N-type impurity diffusion component to a surface of the semiconductor substrate, and causing the N-type impurity diffusion component to diffuse from the applied diffusing agent. Specifically, a thermally oxidized film is first formed on a surface of a semiconductor substrate, and subsequently a photolithographic method is used to laminate a resist having a predetermined pattern onto the thermally oxidized film. The resist is used as a mask to etch, with an acid or alkali, regions of the thermally oxidized film that are not masked by the resist, and then the resist is peeled to form a mask of the thermally oxidized film. A diffusing agent which contains an N-type impurity diffusion component is applied thereto, thereby forming a diffusion film in regions in which openings in the mask are positioned. The regions are heated to a high temperature to cause the diffusing agent to diffuse into the regions, thereby forming an N-type impurity diffusion layer.
In recent years, suggestions have been made about methods of using an ink-jet method to pattern a surface of a semiconductor substrate with a diffusing agent into (see, for example, Patent Literature 1, Patent Literature 2, and Patent Literature 3). In the ink-jet method, the diffusing agent is jetted from ink-jet nozzles to an impurity diffusion layer region for selective patterning. Thus, as compared with conventional photolithographic methods, the ink-jet method does not require any complicated step, and makes it possible to make a pattern easily while also reducing the amount of liquid to be used.